Remove dynahash.h

All the callers of my_log2() are now limited inside dynahash.c, so let's
remove this header.  The same capability is provided by pg_bitutils.h
already.

Discussion: https://postgr.es/m/CAEZATCUJPQD_7sC-wErak2CQGNa6bj2hY-mr8wsBki=kX7f2_A@mail.gmail.com

src/backend/utils/hash/dynahash.c

@@ -102,7 +102,6 @@
 #include "port/pg_bitutils.h"
 #include "storage/shmem.h"
 #include "storage/spin.h"
-#include "utils/dynahash.h"
 #include "utils/memutils.h"
 
 
@@ -281,6 +280,7 @@ static bool init_htab(HTAB *hashp, int64 nelem);
 pg_noreturn static void hash_corrupted(HTAB *hashp);
 static uint32 hash_initial_lookup(HTAB *hashp, uint32 hashvalue,
 								  HASHBUCKET **bucketptr);
+static int	my_log2(int64 num);
 static int64 next_pow2_int64(int64 num);
 static int	next_pow2_int(int64 num);
 static void register_seq_scan(HTAB *hashp);
@@ -1813,7 +1813,7 @@ hash_corrupted(HTAB *hashp)
 }
 
 /* calculate ceil(log base 2) of num */
-int
+static int
 my_log2(int64 num)
 {
 	/*

src/include/utils/dynahash.h

@@ -1,20 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * dynahash.h
- *	  POSTGRES dynahash.h file definitions
- *
- *
- * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- * IDENTIFICATION
- *		src/include/utils/dynahash.h
- *
- *-------------------------------------------------------------------------
- */
-#ifndef DYNAHASH_H
-#define DYNAHASH_H
-
-extern int	my_log2(int64 num);
-
-#endif							/* DYNAHASH_H */